No big mystery. I'm just using "positive" time to mean what it usually means: the direction of time that our clocks go forward. --Dan << Re time reversal: The fact that in our neighborhood in spacetime we see stars radiating only in positive time -- and all the entropic consequences of this -- is usually attributed to initial conditions, not to any actual "law" of physics. (The Ehrenfest urn model is usually considered a good microcosm of thermodynamics, and shows time reversal symmetry.) It's just a guess, but it seems likely to me that we are aware of only a small or infinitesimal fraction of the universe, and that some other time and place have stars radiating in negative time. [What exactly does this mean? How do you experimentally determine whether your stars are radiating in positive or negative time?
_____________________________________________________________________ "It don't mean a thing if it ain't got that certain je ne sais quoi." --Peter Schickele